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Posted: 3/7/2012 11:18:10 AM EDT
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I'm starting to resize my first batch of .223 brass for my ar15. I'm using once fired brass (from my gun), and a RCBS SB x-die.
I have a Hornady headspace gage and a Dillion case gage. And I've done a lot of reading, and asking questions. The case's headspace is 1.459", so I bump the shoulder back to 1.457". When I do this, it 'fails' the Dillion case gage (too short). But when I put that case in my gun's chamber, I can close the bolt with a slight press on the back of the bcg. I'm assuming the case fired from my gun is a more accurate representation of my chamber than the Dillon case gage, therefore it's a better 'gage' of what's going on. So, I plan on bumping the shoulder back 0.002" and let her rip- regardless of what the case gage says. Something else that I wasn't expecting; my fired cases 'pass' the Dillon case gage before sizing? I feel like a dog chasing its tail. Can we have a friendly discussion about if I'm going about this in the right way. |
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The Dillon gage isn't 1000% accurate. Also - even when I have a lot of brass with the same headstamp and number of firings, the headspacing between rounds isn't identical after sizing - nor is length after trimming. It's just - close. I try and keep the deviation range within max/min specs but even after 10 years of loading, I can't do it.
What I do is make three piles. 1. Ones that pass headspace gaging. (Between high and low) 2. Ones that don't and aren't unsafe to fire. (Flush with the high step or low step or brass slightly higher/lower than high/low step) 3. Ones that are unsafe to fire. (They get pulled) I shoot all of the ones in group 2 first during training - never had a problem. For my 3-gun major match ammunition - all must pass with no sort of defect, cosmetic or otherwise. All are visually inspected one at a time by hand. |
Brass can get shorter on firing, when measuring from head to datum. If you look at the SAAMI drawings/measurements, 1.4596" is the minimum for the ammo when new or brass resized. But a minimum chamber can be as tight as 1.4636" Your rifles chamber is your best gauge.  http://www.saami.org/PubResources/CC_Drawings/Rifle/223%20Remington.pdf
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My fired cases "pass" my Dillon case gage. Rifle case gages aren't faux chambers like the pistol case gages are. They only measure two things: OAL and headspace, not whether it'll chamber or not That being said, you may have a tighter or looser chamber than what the case gage is made to test, e.g. a "standard" .223 chamber. I'd trust your bbl when it comes to sizing, but only for that gun. Brass sized and prepped for that barrel I wouldn't trust in another gun especially when it falls out of spec on the Dillon case gage. If you want to see if the Dillon gage is out of spec, drop 2 or 3 different makes of factory rounds in it and see if they're higher or lower than the max and min steps of the gage. If all 2 or 3 are within the high and low steps of the gage chances are pretty the gage is on spec. Do an alternate test, use your bullet puller to pull a factory round, dump the powder, and see how it chambers in your rifle compared to your reloads |
| What is your rifle chambered in and what chamber is the case gage for? Is there any chance that you are sizing for a .223 and have a case gage for 5.56? Since a .223 headspace is slightly smaller than a 5.56 headspace I wonder if that could cause your discrepancy. I have also heard of a wide variation in the Dillon gages. Do you know anyone that has their own Dillon gage to test your rounds in? |
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Do this test and report results back to us.
Take a piece of fired brass (fired in your gun). Insert it in the chamber and try to close the bolt (BCG). Does it close? If it does, the fired brass does not fully represent the dimensions of your chamber.It has "sprung back" and is slightly under-sized. If you cannot close the bolt, or not without pushing noticably harder than after sizing, then the brass does reasonably represent your chamber dimensions and your 0.002" set back is probably the right thing to do. Just for the record, I place little to no value in the various "case gages" that are out there for rifle reloading. Even the Stoney Point/Hornady gages have to be used properly to give good data. Still, the SP/H is the one I prefer, by far. The RCBS Precision Mic is in the middle but it's too easy to get bad data using that gage. It's too dependant upon having the right "touch" and it is pretty easy to change the reading by several thousandths (mils) when you're trying to measure a set back of only a few thousandths (mils). |
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I have an RCBS Precision Mic and measured my fire formed brass. The average showed that my fire formed brass was about -.002 average under ANSI minimum spec for .223 remington. Is this bad by not falling between the minimum/Maximum ANSI?
Before I used to full length resize without measuring with a gauge like this. Now I can size brass to be between -.001 to .-.002 below my fire formed brass measurement. AM I correct in assuming that not only would bumping the shoulder back that much would not only help case life but help in accuracy? I measure some full length sized brass I made before getting the RCBS Mic and I was getting -.005 under ANSI minimum. I read somewhere that one should check the RCBS Precision MIC by putting a headspace gauge that can measure it to determine if it is a bit "off". |
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Quoted:
Do this test and report results back to us. Take a piece of fired brass (fired in your gun). Insert it in the chamber and try to close the bolt (BCG). Does it close? If it does, the fired brass does not fully represent the dimensions of your chamber.It has "sprung back" and is slightly under-sized. If you cannot close the bolt, or not without pushing noticably harder than after sizing, then the brass does reasonably represent your chamber dimensions and your 0.002" set back is probably the right thing to do. Thanks! I did what you mentioned, and the highlighted red is the result. |
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Also remember that the Hornady headspace gage doesn't give a actual headspace measurement as the bushing doesn't really fall on the datum line on the shoulder.
It is really to be used as a reference point. What I do is find a piece of fired brass that is the size of my chamber and then use this in the hornady headspace gage and then zero my calipers with this case. Then just place your sized cases in the Hornady gage and it will tell how many thou + or - you are from your reference case. |
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My 1x fired cases from my AR-15 measure 1.463", I bump them back to 1.460" and they pass the Dillon case gauge. Measured on a Hornady headpspace gauge.
All my resized brass is +/- 0.001" of the 1.460" set point. I trim with a Dillon power trimmer mounted to my press and all my cases trim to +/- 0.02". I use a Redding resizing die w/carbide expander and RCBS or Dillon Spray lube. I have found this combo of things gets the most consistant results across a 1,000 round spread. -Masta |
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Quoted:
My 1x fired cases from my AR-15 measure 1.463", I bump them back to 1.460" and they pass the Dillon case gauge. Measured on a Hornady headpspace gauge. All my resized brass is +/- 0.001" of the 1.460" set point. I trim with a Dillon power trimmer mounted to my press and all my cases trim to +/- 0.02". I use a Redding resizing die w/carbide expander and RCBS or Dillon Spray lube. I have found this combo of things gets the most consistant results across a 1,000 round spread. -Masta Gee I find this interesting as my fire formed cases from my AR come out to 1.4565" measuring with my Hornady headspace gage. This measurement of 1.4565" comes out to about .0025" above the top step of my Dillon case gage. I am bumping back the shoulders of my brass 0035" to 0045" for an optimal measurement of 1.4525" I am shooting a Colt AR with a 5.56 Nato chamber. |
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Quoted:
Quoted:
My 1x fired cases from my AR-15 measure 1.463", I bump them back to 1.460" and they pass the Dillon case gauge. Measured on a Hornady headpspace gauge. All my resized brass is +/- 0.001" of the 1.460" set point. I trim with a Dillon power trimmer mounted to my press and all my cases trim to +/- 0.02". I use a Redding resizing die w/carbide expander and RCBS or Dillon Spray lube. I have found this combo of things gets the most consistant results across a 1,000 round spread. -Masta Gee I find this interesting as my fire formed cases from my AR come out to 1.4565" measuring with my Hornady headspace gage. This measurement of 1.4565" comes out to about .0025" above the top step of my Dillon case gage. I am bumping back the shoulders of my brass 0035" to 0045" for an optimal measurement of 1.4525" I am shooting a Colt AR with a 5.56 Nato chamber. As I am right in the middle of this with a RCBS die not sizing enough I can say that my headspace one once fired is also 1.463 and I am bumping them back to 1.460 as measured with the Hornady gear. I will have a Dillon gage in a couple days to check out. As posted in another post I am having trouble with a die and will need to check a few cases. |
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